Our objectives in the proposed research are to determine the atomic three-dimensional structures of specific proteins of biomedical interest and to develop procedures that will speed the analysis by, enhance the quality of results from, and broaden the realm of applicability of x-ray diffraction methods. These studies will use the methods of protein crystallography with a special emphasis on anomalous-scattering techniques. The proposed work is an outgrowth of our recent discoveries of hitherto unrealized potential for anomalous scattering in structure determination. We specifically propose (1) to develop the methodology for making effective use of anomalous scattering in analyzing the crystal structures of protein molecules, (2) to apply the method of anomalous-choice phasing that we developed for analysing crambin to other crystalline native proteins that contain anomalous scatterers, (3) to apply the anomalous-choice phasing method to crystalline heavy-atom complexes of proteins and (4) to perform multiple-wavelength experiments using synchrotron radiation near the absorption edges of specific anomalous scatterers in protein crystals. We will seek to innovate and improve methods in the course of solving interesting biological problems. The specific proteins that we plan to study include hemerythrins, sillucin, ubiquitin, ribonuclease, lamprey hemoglobin and uteroferrin.